1. Technical Field
The present disclosure relates to a monitoring system, and more particularly to a system that monitors forces between bearing surfaces.
2. Related Art
Some medical conditions may result in the degeneration of a human joint, causing a patient to consider and ultimately undergo joint replacement surgery. The long-term success of the surgery oftentimes relies upon the skill of the surgeon and may involve a long, difficult recovery process.
The materials used in a joint replacement surgery are designed to enable the joint to move like a normal joint. Various prosthetic components may be used, including metals and/or plastic components. Several metals may be used, including stainless steel, alloys of cobalt and chrome, and titanium, while the plastic components may be constructed of a durable and wear resistant polyethylene. Plastic bone cement may be used to anchor the prosthesis into the bone, however, the prosthesis may be implanted without cement when the prosthesis and the bone are designed to fit and lock together directly.
To undergo the operation, the patient is given an anesthetic while the surgeon replaces the damaged parts of the joint. For example, in knee replacement surgery, the damaged ends of the bones (i.e., the femur and the tibia) and the cartilage are replaced with metal and plastic surfaces that are shaped to restore knee movement and function. In another example, to replace a hip joint, the damaged ball (i.e., the upper end of the femur) is replaced by a metal ball attached to a metal stem fitted into the femur, and a plastic socket is implanted into the pelvis to replace the damaged socket. Although hip and knee replacements are the most common, joint replacement can be performed on other joints, including the ankle, foot, shoulder, elbow, fingers and spine.
As with all major surgical procedures, complications may occur. Some of the most common complications include thrombophlebitis, infection, and stiffness and loosening of the prosthesis. While thrombophlebitis and infection may be treated medically, stiffness and loosening of the prosthesis may require additional surgeries. One technique utilized to reduce the likelihood of stiffness and loosening relies upon the skill of the physician to align and balance the replacement joint along with ligaments and soft tissue intraoperatively, i.e., during the joint replacement operation.
During surgery, a physician may choose to insert one or more temporary components. For example, a first component known as a “spacer block” is used to help determine whether additional bone removal is necessary or to determine the size of the “trial” component to be used. The trial component then may be inserted and used for balancing the collateral ligaments, and so forth. After the trial component is used, then a permanent component is inserted into the body. For example, during a total knee replacement procedure, a femoral or tibial spacer block and/or trial may be employed to assist with the selection of appropriate permanent femoral and/or tibial prosthetic components, e.g., referred to as a tibia insert.
While temporary components such as spacers and trials serve important purposes in gathering information prior to implantation of a permanent component, one drawback associated with temporary components is that a physician may need to “try out” different spacer or trial sizes and configurations for the purpose of finding the right size and thickness, and for balancing collateral ligaments and determining an appropriate permanent prosthetic fit, which will balance the soft tissues within the body. In particular, during the early stages of a procedure, a physician may insert and remove various spacer or trial components having different configurations and gather feedback, e.g., from the patient. Several rounds of spacer and/or trial implantation and feedback may be required before an optimal component configuration is determined. However, when relying on feedback from a sedated patient, the feedback may not be accurate since it is subjectively obtained under relatively poor conditions. Thus, after surgery, relatively fast degeneration of the permanent component may result.
Some previous techniques have relied on using sensors that are coupled to a temporary component to collect data. In some systems, the sensors are positioned underneath a portion of the monitoring device's surface that has been removed and replaced (e.g., a plug). In such systems, the integrity of the structure may be compromised as a result of plug. This may result in the monitoring device generating false and/or inaccurate measurements. Other systems require a physician to perform a number of different tests to obtain usable data.
Therefore, it would be desirable to obtain enhanced feedback during prosthesis fitting and balancing in joints without increasing the burden imposed upon the physician or the patient. Thus, there is a need for a force monitoring system that will provide enhanced feedback during prosthesis fitting and balancing.